Conventionally, an existing computer environment may be migrated to a different computer environment for performance improvement, load distribution, and/or maintenance. The computer environment may be a real computer environment or a virtual computer environment executed by a virtual machine (VM) monitor. In the migration of the computer environment, data on a disk of a source computer environment are copied to a disk of a destination computer environment.
As a copying technology, postcopy is disclosed that enables data on the source environment to be referred to from the destination environment transparently as if the data are at hand, and when data that have not yet been copied to the destination are referred to, copies the data from the source to the destination.
For example, Japanese Laid-Open Patent Publication Nos. 2008-33500 and 2008-33483 disclose a technology for migration of computer environment using postcopy in which a module that controls postcopy of data divides data to be migrated into first data used at the start-up of an operating system (OS) and remaining second data.
The module migrates the first data to the destination computer environment where the OS is started up using the copied first data to resume the execution of a task. If the OS on the destination requires a part of the second data that has not yet been copied, the module copies the data on an on-demand basis as well as copying the second data in background, thereby migrating the computer environment.
However, the conventional technology described above assumes that the destination computer environment/VM monitor includes a module for postcopy in advance. Thus, migration using postcopy is difficult for an existing computer environment that does not include the module for postcopy.